In order to implement eco-friendly technologies and to solve problems such as energy exhaustion and the like, electric vehicles are recently emerging. An electric vehicle is operated using a motor that is supplied with electricity from a battery and outputs power, and accordingly, since the electric vehicle has advantages in that it does not discharge carbon dioxide, generates very little noise, and has higher energy efficiency of the motor than that of an engine, the electric vehicle is highlighted as the eco-friendly vehicle.
However, unlike that conventional vehicles using an internal combustion engine to heat a cooling water by a heat source generated from the engine, the electric vehicle that does not have a separately installed engine therein does not heat the cooling water by the heat generated from the engine.
Therefore, an apparatus for heating the cooling water should be separately provided, but according to the related art, a temperature of a sheath heater was controlled and overheating thereof was prevented by applying a temperature sensor to a circuit unit. However, in a case in which a controller or a sensor of the circuit unit fails, since the circuit unit does not control a flow of current of the sheath heater, the sheath heater was overheated and damaged.
The matters described as the related art have been provided only for assisting in the understanding for the background of the present disclosure and should not be considered as corresponding to the related art known to those skilled in the art.